What might account for a soldier experiencing syncope after standing at attention for a long period of time?
Increased respiratory rate.
Vasoconstriction.
Increased heart rate.
Venous pooling.
The Correct Answer is D
Choice D rationale
Venous pooling, particularly in the lower extremities, commonly occurs when standing still for prolonged periods due to the effects of gravity and reduced skeletal muscle pump activity. This pooling decreases venous return to the heart, leading to reduced cardiac output and consequently a drop in cerebral blood flow, which can result in syncope (fainting).
Choice A rationale
Increased respiratory rate (hyperventilation) typically leads to a decrease in carbon dioxide levels, causing respiratory alkalosis. While severe hyperventilation can lead to cerebral vasoconstriction and lightheadedness, it is not the primary physiological mechanism for syncope after prolonged standing.
Choice B rationale
Vasoconstriction, particularly systemic arteriolar vasoconstriction, would generally help maintain blood pressure by increasing total peripheral resistance, counteracting a drop in blood pressure. Therefore, it would typically prevent rather than cause syncope in this scenario, unless it was a compensatory, insufficient response.
Choice C rationale
An increased heart rate is a compensatory mechanism to maintain cardiac output when venous return or stroke volume is reduced, such as during orthostatic stress. While the heart rate does increase, it is often insufficient to prevent the fall in blood pressure that leads to syncope if venous pooling is severe.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
Choice A rationale
Positive feedback mechanisms amplify the initial stimulus, leading to an increased response. While important in certain physiological processes like childbirth (oxytocin release) or blood clotting, it is less common for target organs to regulate pituitary function through this method, as it can lead to instability.
Choice B rationale
Negative feedback is the predominant mechanism by which target organs regulate pituitary function. High levels of target gland hormones inhibit the release of stimulating hormones from the pituitary and hypothalamus, thus maintaining hormonal homeostasis and preventing overproduction or underproduction.
Choice C rationale
Neural stimulation involves direct nerve impulses influencing hormone release, as seen in the adrenal medulla's response to sympathetic nervous system activation. While the hypothalamus has neural connections to the pituitary, direct neural stimulation from target organs is not the primary regulatory mechanism for pituitary control.
Choice D rationale
Direct hormonal release from target organs without involving feedback loops would result in unregulated hormone secretion, disrupting endocrine balance. Target organs typically release hormones that, in turn, exert feedback effects on the pituitary or hypothalamus, ensuring precise control and preventing dysregulation.
Correct Answer is B
Explanation
Choice A rationale
Antidiuretic hormone (ADH), also known as vasopressin, is synthesized in the hypothalamus and subsequently released from the posterior pituitary gland. Its primary function involves regulating water balance by increasing water reabsorption in the renal collecting ducts, thereby concentrating urine and preventing dehydration.
Choice B rationale
Luteinizing hormone (LH) is a gonadotropic hormone produced and secreted by the anterior pituitary gland. In females, it triggers ovulation and corpus luteum formation, while in males, it stimulates testosterone production by the Leydig cells. It is not synthesized in the hypothalamus.
Choice C rationale
Thyrotropin-releasing hormone (TRH) is a hypothalamic hormone that stimulates the anterior pituitary to release thyroid-stimulating hormone (TSH) and prolactin. This tripeptide hormone plays a crucial role in regulating thyroid function and lactation through its signaling pathways.
Choice D rationale
Somatostatin, also known as growth hormone-inhibiting hormone (GHIH), is a peptide hormone produced in the hypothalamus. It inhibits the release of growth hormone (GH) and thyroid-stimulating hormone (TSH) from the anterior pituitary, playing a vital role in neuroendocrine regulation and metabolism.
Choice E rationale
Prolactin-inhibiting hormone (PIH), primarily dopamine, is synthesized in the hypothalamus. It continuously inhibits the secretion of prolactin from the anterior pituitary gland, thus regulating lactation. A decrease in PIH allows for increased prolactin release, promoting milk synthesis.
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